1. Field of the Invention
The present invention relates to a high-performance wide-angle aspheric zoom lens used for a video camera or the like, having a zoom ratio of approx. 3, a half angle of view of approx. 40.degree. at the wide-angle end, and aberration correction.
2. Related Art of the Invention
High image quality and high performance as well as operability and maneuverability are being demanded from the latest video cameras. Because of this, 1/3 inch high-resolution imaging devices have become popular and 1/4 inch imaging devices are now being developed. Thus, these devices have contributed to the decrease in size and weight of video cameras. In addition, a compact, lightweight high-performance wide-angle zoom lens with a large aperture ratio is strongly in demand. Moreover, a decrease in cost is also strongly desired. Therefore, it is necessary to develop a high-performance wide-angle zoom lens comprised of fewer lenses that is machinable and has superior mass production characteristics.
For a high-magnification wide-angle zoom lens, however, the outside diameter of the lens closest to an object increases; moreover several lenses are required to achieve high aberration correction. The size, weight, and price of the zoom lenses increase and therefore zoom lenses cannot be used in consumer video cameras.
For compact and lightweight zoom lenses with a zoom ratio of 2 to 3 and comprising fewer lenses, a two-group zoom lens is frequently used which zooms an object by arranging a lens group with a negative refracting power at the object side and a lens group with a positive refracting power at the image side and changing the distance between both lens groups. For example, the two-group zoom lens disclosed in U.S. Pat. No. 5,155,629 has a zoom ratio of approx. 3, a half angle of view of 27.degree. to 9.degree., and an F number of 2.8 to 5.7, comprising 7 to 8 lenses. The two-group zoom lens disclosed in Japanese Patent Publication No. Hei 3-16004 has a zoom ratio of approx. 2, a half angle of view of approx. 38.degree. to 17.degree., and an F number of 4 to 4.5, comprising 10 lenses.
However, the existing two-group zoom lenses having the above constitution cannot simultaneously have a zoom ratio of approx. 3, a half angle of view of approx. 38.degree., and an F number of 2 because the lens comprises a small number of lenses.